If you already filed your tax return, you do not have to amend it for the $10,200 unemployment exclusion. The IRS is going to recalculate your tax return and send you the additional refund. It might take several months to get it. For details see the following IRS announcement.

IRS to recalculate taxes on unemployment benefits; refunds to start in May

See this from the IRS    https://www.irs.gov/newsroom/irs-to-recalculate-taxes-on-unemployment-benefits-refunds-to-start-in-m...

and this FAQ

https://ttlc.intuit.com/community/internal-revenue-service/help/how-is-my-state-taxing-unemployment-...