What do I do if I'm still getting pain 4 weeks after varicose vein operation?

Pain. i would discuss with the md that performed the procedure to try and figure out the source of the discomfort.
Check in. With the doctor who did the procedure. Can be normal but need to check for infection or blood clots in veins that were not treated.
Depends. You may still have pain in the residual varicose veins. If that is the case then those veins need to be treated as well. I would discuss this with your doctor.