Update:
He drilled an 1/8th" hole in the truss to help drain fluid that may collect in it during water crossings. My whole reasoning for solid welding it just went out the window. I was trying to avoid rusting out the inside of the truss. Ah, well. Live and learn!!!!
You could weld up the hole or tap it and put in a plug, but if your confident that your welded up solid all around the truss, I would just weld the hole and forget it..unless you live in a real humid state maybe I would do the plug...