I had this problem too, clutch plates stuck. First warm up the engine. Sit on bike while in gear (not running) and engage the clutch lever then rock back and fourth and see if it will free it.
My dad years ago told me to hold the clutch lever in with a wire wrapped around it and walk away, come back in a day an try the rocking again.
Some may say this weakens the clutch springs?
I always thought week clutch springs are better than no clutch at all.
This has worked for me many times.