Hello Doctor.. Two Years Ago I Was Standing At A

Hello doctor.. two years ago I was standing at a bus stop I felt someone poked me something on my back suddenly wen I turned back the person went away... I'm not getting whether he came to pick up my wallet or to intentionally pick me out something like needle... now I'm really worried for hiv... I used to get only cold once a two or three months...plz help me I'm really scared