Muscle twitch under the bottom right ribcage. started last night still here this morning. painless but annoying. what cause? how stop?

Fasciculation: What you describe is likely a fasciculation (muscle twitch) which is a small, local, involuntary muscle contraction and relaxation that may be visible under the skin. Most all healthy people experience however typically infrequent. Causes can be from stimulants such as caffeine, sudafed, albuterol inhaler. They often occur during a rest period after sustained stressed/exercise (tense muscles).