If it’s isolated to one single sink, it’s likely a calcium build up and you should wait until a plumber arrives.
If there’s no hot water, it could be a breaker that needs resetting until a plumber can arrive to diagnose it further.
Don’t try to fix the issue yourself. This could make things worse and wind up costing you more in the long run.
Do clean up the affected area(s) around where your plumber will be working.