I'm sure that your upper is a M16 upper, yes there are AR15 only uppers and M16 uppers. The M16 uppers have a relief cut for the sear and if you tried using a AR15 upper with out the sear relief you would have a bunch of issues.

Anyway, the bolt may have contacted the sear but should be fine. Think about RDIAS, they are always in the "auto" position that a regular sear flips to when you put the selector to auto.

bottom line should be fine.