This is not normal. I had bruising and tenderness after my ablations but nothing like this. And the fact that you healed up normally and now this flared up, it needs to be checked. Don't worry about what they think in ER. This is not in your imagination. Please go.
Please get yourself to the ER. When I developed a clot after having surgery I had no swelling or redness infact all I had was an ache in my leg. The blood test was only slightly over the recommended and the Ultrasound test was needed. They found a small clot near my ankle. If you get it sorted straight away you won't have too many issues after that.
Were you not taking low dose asprin after your ablation?
Call your doctor, please.
I don't believe this is a normal phenomonon at 3 weeks post ablation. I was given explicit instructions to observe this area for tenderness, swelling, abnormal pain, warmth in the area of the puncture site, as well as coldness and tingling in the leg. These can be signs of infection and or clotting. I don't want to alarm you, but this is something you don't want to mess around with. Please call you doctor immediately for instruction on what you should do!