Legal advice on validity of marrying second cousin.

Atul Garg, please provide details like the place which you belong to, your caste etc so that our experienced members can give you a convincing answer.

Both of you are covered under the sapinda relationship prohibiting both of you to go further with the alliance under the Hindu Marriage Act. However, you may escape the prevalent rule if you are aware of the conventions being followed in your society taking even the consideration of the cast culture.
You need to abide by such rules since any violation of such rules will lead to tension between you and your would be partner. This may create disruption within your family life.
Now you need to consider the birth defects arising from such a close relationship ( bride being your second cousin)
You need to have a consultation with a specialist confirming any abnormality in relation to genes factor apart from other tests such as ECG test, Kidney Function Test, Liver Function Test and other tests as decided by the specialist to know well-being of both of you.
Normally genes defects are observed in some cases while marrying the second cousin though in rare cases. This test is required for your own safety.
If both of you are satisfied with your medical reports apart from acceptance of the society, you can tie the knot. Take the consultation of the lawyer.

As suggested by the Lead Editor, if you could elaborate on the matter by telling whether in your tribe or community such marriages are permissible, then it would have been easier for us to give a better opinion. Anyway, being a close relation the relationship falling under the Sapinda category is legally not allowed until it is in practice in the community of the parties involved. So, considering that you have to go ahead in the matter.

As such the relationship is not a taboo altogether. In many communities and geographies, such marriages are permitted and practised. You have to consult your elders and well wishers whether this is accepted in your community/family traditions and also by the society in the place you are living.
In families which follow the patriarchal system the family lineage transmits by father's side. As the parents al ancestors are not male(brothers) this is accepted in many communities.
So before jumping into any hasty action, you both consult your elders and well wishers and do as per their considered advice. My preliminary guess from whatever information given is that there may not be major issues, unless you know there are issues.

If there is such acceptable tradition and practice, then you can go for traditional marriage.

Some decisions are taken or rules are made on the basis of different communities and particular places of residence. Your relationship is not restricted to marriage, but still, it is most important that you get more information about your local rules from your family members or other people of your society. Marriage is an important decision and naturally, you will always want to be with the person you love but family is an important part. As you mentioned that your relationship is already a family relationship, so I don't think you will have much difficulty in getting information. There are many such practices or rules in some societies where marriage can take place in this type of family relationship. As far as legal permission is concerned, when the customs or rules of the community have been going on for a long time, they are recognized for law. Agreeing is an important part of the family, so your first love should be in the direction of how your loved ones view and adopt this relationship.

Marriage between cousins is not illegal. This kind of marriage is customary and acceptable in many parts of India. But it is taboo in some other regions. Moreover, siblings born out of these couples may face some genetic disorders in rare cases. The most important aspect is the determination of persons going to be married. If they strongly feel about going ahead with the marriage, it is well and good.