Asus board by any chance? Even if it isn't, yes, a fair amount of force is ok as long as the CPU is properly in the socket. Asus boards seem to be notorious for this though. Mine was, for sure. Also, since it's LGA 1155 it's the same for Sandy and Ivy in that respect.
Yep, my socket plate even made a slight "creaking" noise as I brought the lever down. This would have worried me a little, but as long as you drop the CPU in the socket in the right orientation, it should be held in place firmly at the notches.