Seized caliper. Either rebuild it yourself or go to AutoZone and get a rebuilt one for $50. IMHO the price-to-labor ratio of buying a rebuilt caliper vs. doing it yourself is completely worth it. That'll solve your problem.
You should do both since they're a pair, but you can get away with one if you want.
SEE SIG, DOGE IT ALL
My opinion is the opposite of your opinion, even if you change your opinion to my opinion.