How do we get hot water coming out of bathroom shower ? The faucet only allows cold water to come out on left and on right nothing at all

Is this a single handle or 2. Hot is usually on the left on 2 handle faucets. Did this all of a sudden just happen? Other hot water faucets OK. Could be dirt/debris in the supply hole in the cartridge if a 1handle and possibly a deteriorating dip tube in the HW heater.

Like ma041 said: each tube, in a lot of sinks contain tiny filters in it, and there is usually one at the spout of the faucet. Also make sure the 2 or 1 supply velves are on (counter-clockwise all the way).