I have this pain in my left upper forearm ,underneath, opposite the elbow. it only hurts when i do side latural with 30lbs or more or when i,m trying to swing a dumbbell up to do any kind of overhead press. it also hurts when i do curls,but once a do a set or two it seems to get better . as for the presses it does hurt to do the actual exercises. i don't know if this a pulled tendon or what, otherwise in everyday normal life(yeh right) it doesn't bother me.
Probably strained your brachioradialus muscle,sort an extension of your bicep. Hard to tell more without knowing what motion caused the original injury. Go light and let it heal.
It sound like your alnar nerve (spelling). I had the same problem a couple of years back. Give it a rest for a few weeks. try taking an antiflammatory. I'm not a doctor so it may be best if you visit your family practioner.