I forgot to enter 1099SA.Do I need to amend it?Filled standard deduction.Will it affect my refund/payment to IRS or Maine?What's the difference between 1099SA and 5498SA?

Second question first - A 5498SA is an informational form for taxpayers that is not entered on you tax return.  It is also filed with the IRS.  It shows the amount that was contributed to your HSA, and the ending balance of your HSA.  You don't need to do anything with this form.  

A 1099-SA reports distributions from one of the following:

• Health savings account (HSA).
• Archer Medical Savings Account (Archer MSA).
• Medicare Advantage Medical Savings Account (MA MSA).

If you didn't enter your Form 1099-SA, then you probably didn't include the amount that was paid towards qualified medical expenses.  In this case, the IRS will see the distribution from the HSA (or other plan) and assume that none of the proceeds were used to pay qualified medical expenses, add it to your taxable income and send you a notice of proposed change to your tax return and a bill for the additional tax due.

I recommend you file an amended return and add your Form 1099-SA.  To do so, click on the following link for instructions: How do I amend my 2019 TurboTax Online return?