I Had Scleratherapy Done Around my Ankle, Which is a Sensitive Area. It is Still Swollen After 3wks?

I would highly recommend that you see your provider for follow-up as enough time has past to still be experiencing pain.  

While the ankle does tend to be a bit more sensitive to sclerotherapy treatment, any sensitivity or soreness should have diminished after 3 weeks. As a sclerotherapy and vein expert, I recommend you see your doctor for a follow-up to ensure there is no more serious complication at play here.

The recommendation from Board Certified Phlebologists (vein specialists) like myself is to get an urgent Doppler ultrasound evaluation to make sure you don't have a deep vein clot.

I would expect that the soreness and tenderness would be gone by now.  I would have the area evaluated by the doctor that did the treatment to ensure no complications, such as infection or blood clots.  It may just be continued inflammation (i.e. phlebitis) as the veins respond to the treatment, but all of this is typically gone by 3 weeks.  There are more nerves in the region of the foot and ankle than there are in the leg, so the risk of persistent nerve pain is higher when the ankle and foot are treated.

The most sensitive area for sclerotherapy seems to be around the ankles probably because there is only skin and bone there and not enough fat to serve as a cushion.  Because of this I have found sclerotherapy to be uncomfortable in this area but I have not seen the soreness last for 3 weeks post treatment.  I would be concerned that there is a reason for the continued soreness such as a clotted vein ( superficial or localized deep vein phlebitis) or skin sensitivity secondary to leakage of the sclerosing solution into the surrounding tissue.  You should follow up with your treating physician.