I'm on antibiotics for tonsillitis and almost done with them, but my lymph node behind my left ear is sore and has a bump in it what can I do?

Lymohadenopathy. This lymph node has been doing its job and the enlargement engendered while helping to contain your tonsillar infection is producing the tenderness you are experiencing. This should recede and become non-tender in time, but if not, then seek medical assistance. Good luck, .