What's rhe brand name of your shower valve? You may have disturbed some minerals built up in the pipe walls that's now clogging the inlet ports of your cartridge.
Turn the water off and remove the cartridge, Check and clean the inlet ports. Now while the valve is open, turn the water back on for a moment to flush out the lines. Reassemble and test. Better now? Good luck, Tom

You could have also disturbed the anti scald setting pin (if so equipped) and you can't move the handle far enough to the hot side.