May want to try pushing fore end forward and try pulling trigger again to ensure it was in battery, pointing in the safest direction of course, then try bolt release to see if that helps, otherwise give it a sharp blow with your palm as you turn it over in your hands on the sides and top and bottom of the receiver possibly unjamming something that has broken or gotten in the action.
This may have already been tried, but I usually go to the simplest and safest things first. After that, if it is still jammed follow the advice previously listed as to disassembling the gun.
The 37 can be a bitch to reassemble if you aren't familiar with it!
