Did Badminton cause it?
Have you tried using a lighter or head light racquet?
Have you tried a larger grip on the racquet?
Has the physio given you any exercises to do? It’s quite worrying if they haven’t given you any exercises to do to make it better.
I’m seeing one for tennis elbow pain and they have been very knowledgeable so far.
They’ve done massages, given me several exercises to try, told me about K-Tape (probably won’t help with your injury), braces etc.
Have you tried using a “powerball” ? It’s a hand held device with a gyroacellerometer in it. You start it by pulling a cord, and grip it in one hand and move it in circles to keep it spinning or make it spin faster. Good for strengthening wrist / fingers.