I wasn’t claimed as a dependent but I accidentally put I can be claimed. Will I still get a stimulus check? Or will I hav too amend my return?

If you marked that somebody will claim you, you will not get a stimulus check until you amend your return.

Once your return is accepted and the finances are settled, you can file an amended return. See how to file an amended return.

Three weeks after you mail your amended return securely with tracking, visit track an amended return 

See also, I need to amend my state return.