I ran the first time in years last week, tues-thurs now my left knee is in constant pain what can i do for the pain?

Knees trauma-chronic: He is not young .He has not jog and he should have cautiouly started ---slowly -time and distance of jogging now best is rest-no more running for 4 weeks, do local j =heat /.., cold care analgesic balm supportive ace bandage or orthosis at knee if need use cane on i njured side .Take oral medicine get xray of knees for structural damage do strenthning exercises for quadriceps.