Holy clogged milk duct! It ends up that I had a clogged milk duct. I had a hard time getting a hold of anyone, it being Friday at 4pm, on a holiday weekend.... But a good friend of mine has been through thrush, mastitis, etc... So she stopped by and said that's what it looked like.
I put some hot compresses on it, pumped, BF, and even took a pair of tweezers to it (not my proudest moment, but in desperation) and it worked. It felt so much better almost immediately. It's still a little sore today, but by far better than yesterday.
Thanks Jersey and Moesten for your advice!
Re: f/u to BF pain