I forgot to put form 1099-SA but my return already been submitted what can I do to add it? The gross distribution is 101.38 will it make different to my return

Although the amount is very small, please report the Form 1099-SA. IRS has a copy of it and will be looking for it on your tax return. If the funds were used to cover your qualified medical expenses, it will not make a difference on your return.  You will be showing that the amount is used "correctly" and it is not taxable.

If the return has been e-filed and accepted, you can only make the change by amending your tax return. The 1040X for amending 2015 returns will not be available until mid-February.  You should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared.

If your return is e-filed but pending - please wait. If it is rejected for some reason, you can make a change then and re e-file.

my tax has been accepted what next?

You can file  an amendment if it makes a difference. Go back and  add it to your return and save it as a new return. See if it changed the amount of the refund/amount owed.

Do I really need to amend if it wont make a difference? It will cost me up to 37 dollars just to add it and I'm getting the standard deduction so it won't even matter.

Yes, you still need to amend.  Even though it doesn't make a difference in your refund, you are reporting that the distribution was used for qualified medial expenses.  If you do not amend, you will eventually get a letter from the IRS stating you did not report this and they will expect tax on the amount of the distribution, plus interest.