My left arm ...?

Has been aching, and feels tender, and "hot" what could it be?My left arm ...?
pinched nerve - see a doctor or physical therapist
Your new tattoo you got the recently?
This could be a lot of things including something as simple as a torn/pulled muscle to an infection in your arm, to something wrong with your heart. Muscles will become warm when they are overused. Have you overused that arm recently? Have you been bitten by a spider and haven't noticed the puncture mark? There are many possibilities as to what is causing your problem. My advice would be to consult a physician as soon a possible.
maybe you slept on it or have been using you arm allot but to cure it you can put some ICE that always works for sore arms or you take some icy hot but i would try the ice first and place a towel around the ice so its not directly on the skin