I realized I made a mistake on my return should I send a check for approximately the difference I am not able to amend the return yet

[KrisD]

Yes, you can do that or pay online. 

Make sure your social security number and "Tax year 2018" are written on your check. 

https://www.irs.gov/payments

[fanfare]

You should not do anything until your return is processed

 the IRS could catch your mistake and fix your return for you
And you don't know what else they might change.