TLDR: Don’t mess about, get it seen to and insist on an ultrasound scan, don’t rely on a blood test.
Minimal swelling and a dull ache for me both times. On the second occasion the blood test gave a false negative and I was told all was well. Developed a PE (clot on the lung) the following week (while ghyll scrambling, not ideal). Straight to A&E, Heparin etc. Fortunately no long term effects (I could blame it for my lack of fitness but it wouldn’t be true). Now on apixaban for life as the rivaroxaban gave me bad reynauds. On the plus side, my BP is now within acceptable limits for the first time ever.
I have had a false alert since. I didn’t feel any shame upon being told I was fine. You can’t mess about with this shit.