How do I remove a mirror modifier, but keep the mesh that's generated by it?

Yello, everyone. Long time lurker, first time poster.

So I was creating a t-shirt for a character… I successfully modelled one (vertical) half of it, and decided to delete the other half and just mirror the half I already made. Anyway, I found out I can’t separately UV map the other half. Is there any way I can remove the mirror modifier, but keep the whole, mirrored mesh that’s created by it? I tried just using a duplicate (shift + D) on the half, but you could see a seam where I rejoined them.

Thanks in advance.

apply the modifier

Whoaaaaa. It works. Thanks!