First of all let's clear your first doubt about tax, as you mentioned that you are not from commerce background and do not have much clarity.
There will not be any tax liability on purchase of second hand machine.
As you said that you will set up a business and use the machine in future in your business, then in such case you can use the same in your business and claim it's worth in your business.
To do so you need to show the machine purchase in your books as an asset and claim depreciation every year @15% from year one. Since you are not very much acquainted with commerce terminology you can take help of some accountant or a practicing CA.
You will have to maintain books of accounts for such claims of expenses. As you have already mentioned that the seller has not provided you any bill for the machine purchased hence you will have to arrange for a bill/invoice of the value of machine or get a agreement drafted for such purchase.
Although you have made one mistake of purchasing the machine before even registering a company or any other entity, which you should have done before purchase of machine and after the company/entity was registered the machine should have been purchased out of funds of company and in name of company only.
Anyway there are always solutions to all problems and it can be managed but you will have to visit a practicing CA for the same and he will help you out for a nominal fees.