Hello and sorry to hear about your leg discomfort. Unfortunately what you're describing sounds like it could possibly be a deep vein thrombosis. This is a classic presentation with prolonged sitting, then lower leg "throbby", or strange pain. The problem is that these clots in the deep veins can let loose and migrate into your lungs and cause problems.
So my suggestion is to go the ER, as much as I'm sure you have better things to do, they can do an ultrasound on your leg and you'll know for sure. These can be quite dangerous, so it's better safe than sorry.
Sorry, I wish I could have told you it was nothing, but there's the possibility it is, so best wishes...
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