Which side to tap on this door hinge?

Get a nice block of wood and put it against the wood frame.  Give it a hard tap with a hammer.   It will not mar the wood frame.  Your problem is not the door.   Your problem is the wood frame that the door sits in is coming unattached from the stud framing of the wall.  In your case, if I understand it, the bottom of the frame has moved because it is loose.  Move the frame with the door in it.  Don't take the door off the hinges.   Now, if that doesn't work, you have to go to the Next Level.  Repositioning a door in the existing framing is remarkably easy to do by removing the face molding on the knocked loose side. (only 1 side, 3 pieces of molding) not both sides) Then cut the nails with an oscillating saw and pull them out with a wire cutter plier.  Push the door back up against the face molding on the other side (which should be straight) and see if everything is  plumb and straight.  If it is, reshim all of the door frame, especially at the hinges and nail the frame to the the wood wall studs.  6 penny finishing nails, nail punch, and a level.

The gap on the hinge side looks pretty even as it should. I doubt there is much you can do to help your problem by hitting on the hinge. It is much more likely that the door jamb on the side opposite the hinge has moved for some reason. You really need to took at that before you start banging on the hinges.

before you do any of this other stuff, LOOK at the screws in the hinges -- loose screws allow the hinge to be loose and thus the door to sag -- causing exactly what you're seeing here.  If the screws will not hold in proper place, you can try the following:  a) next size larger screw as long as the head fits into the hinge properly, b) next increment or two longer screw of same size [depends on what's under the door frame -- can't do this with cbs exterior wall], c) insert a flat toothpick or two into the screw hole and then put the screw back in, using as much force as needed to get it to seat properly into the hinge, d) item c but with the addition of a bit of wood glue on the toothpick -- best to leave this one to last and to let the glue harden up for a couple of hours before reinserting the screw.  -- grampa

Tapping the hinge with a hammer WILL NOT help.

If it has any effect, it will distort the hinge and make things worse.

If you’re saying the left side of the door is rubbing as in the side opposite the hinge, you would hit in the direction of the orange arrow. If you’re saying the top edge of the door is rubbing, hit in the direction of the black arrow.