I was looking over my 2021 return and realized I did not report sale loss disallowed portions for a 1099-B for stocks. It said I owe $12, should I re-file?

You will need to file an amendment for tax year 2021. 

follow the instructions here: How do I amend my federal tax return for a prior year?

I too would suggest filing an amended return.  But, first, did you get a letter from the IRS about it?  If so, then they would have provided a recalculation and an amount to fork over in 30 days and you wouldn't amend your federal return, but you would want to amend your state income tax return if you live in a state that imposes income tax.  

Interestingly, AARP Tax-Aide's tax preparer's guide says to not amend if the difference in income was less than $200.  Instead they ask the taxpayer to simply sit back and wait for a letter.