Hot water pressure is very low on only one faucet?

I turned the water to the house off for @3 hrs. to add outside lines to the front and back decks . When turning it back on hot water pressure was next to nothing in the kitchen sink . the other three were unchanged . Disconnecting the line to the sink thinking there must be blockage found nothing just no pressure . The next day the pressure returned to the kitchen but now in one of the bathrooms have no pressure ..Is it an airlock and what do I do.