Problem uploading to board

I was working on stepper motor program using arduino uno via A4988 driver and there was no motor movement but I heard a whining sound ,So i turned of the motor power supply and was adjusting the potentiometer in A4988 to measure the voltage between pot and gnd (with the arduino board connected to PC)suddenly the RX ,TX pins went off (permenantly)after which i was unable to upload the program to the board and started to get error messages.

avrdude: ser_open(): can't open device "\.\COM3": Access is denied.

Problem uploading to board.

Have I burned my board ,can anyone help me with this problem

Sound like it. But without knowing exactly how you connected everything it's hard to tell.