mossberg model 340BA .22 cal rifle

I have an old Mossberg 22 rifle. Model 340b-a. I took the bolt out for a good cleaning. There is a spring loaded piece of metal that protrudes into where the bolt goes back into.

It neeeds to be retracted rearward in order to put the bolt back in.

Does anyone know how to do it? What is it? I tried to compress it with a screwdriver but there is too much tension on the spring to be effective.

Any suggestions would be appreciated