Occasionally get a pain and sense of tightness in left arm. have occasional high blood pressure. could this be what im feeling? serious?

May be: Occasional high blood pressure readings can be erroneous, measuring technique, size of cuff, timing, position, etc.. Occasional pains in left arm can still be muscular or boby in origin, better get checked by your doctor with more history , better measurements and documentation of vital signs , and routine tests if necessary, preventive health maintenance at any age is important, wish you wellness