Can I give the 12th State board exam again next year

First of all, I would like to thank you to give your valuable time to India Study Channel. You can surely give the State Board Exams next year and score well to improve your percentage. Even if you score less next year, the best out of two marks will be considered. You just need to apply as a private candidate in your State Board and fill the forms and pay the fees next year. I would be able to help you more if you could reveal the State Board name as some rules are different for different state boards.
Also, I would like to suggest you consider private colleges rather than wasting one year as private colleges are also good.
Do not lose hope as life is full of failures and success. Its like a roller coaster giving you ample opportunities to succeed in life.
All the Best!

There is a provision of giving the class 12 exam again for improvement purposes and if one works hard one can secure more marks in the next attempt. Only thing is you lose one precious year of your student life in this endeavour. In such a condition it is imperative that you have to prepare hard with all out efforts in your improvement exam of class 12 as you have to achieve significantly more score than what you have achieved this time.

If you are able to chart out some other career line with your existing score of class 12 then you may not require to go for the improvement exam option. So considering all these aspects you have to take a conscious decision.

You can rewrite your examination with improvement purpose and if you think that one month period to write the examination in the supplementary - stage may not yield effective result, you can take an attempt to rewrite the same in the next year. You have to gear yourself to revise the basics carefully so that you achieve impressive marks in the next time.
With the provision of the best of the two would be taken into consideration for the computing of marks, you will be required to put in best efforts. Even if you don't succeed in achieving higher marks, your existing marks will retain.
Hence to save a year, you may go in a private college for the perusal of your studies and make a fresh move to do better in your MBBS examination.

There is a provision for rewriting all the papers again next year for betterment purpose. As you said one month may not be sufficient for preparing well. So it is wise to appear in the next year examinations. But one important point here is you will waste one year. After that also there is no guarantee that you will get a medical seat. So what I suggest is to get admitted in any good college for B.Sc. You need not attend the classes regularly and you can study your intermediate and entrance test subjects but in case of any adverse results, you can concentrate on your B.Sc. That will save a year for you.
I suggest this to you. Then if you are really interested in MBBS, concentrate on the subjects well and put in good work and work hard, you will be successful.

In the first hand if you are intended to continue with one more efforts in your 12th exam in order to get the required percentage to enable you during the initial selection process via application than it is possible but then do you feel that you are confident and prepared enough to use one complete year?

It's good to note that you are more inclined and attracted with the medical line but on the other side of a coin, I would want you to do some self-introspection of whether or not that you would be able to get the required percentage or else in a way you have taken one complete year for granted which shouldn't have been the scenario.

Now as this has already been clarified on the possibilities, you are still required to have good consultancies from your parents and from your teachers as well on your final stand. Competition is huge and growing and your decision would follow suite when only you are able to stand by it. Best of luck.