What To Do? 🤔🤔

Well I was kinda noticing since last couple of days but I thought I was going crazy. But I was like no he's doing it too often so I was trying to catch him and then I stared him down. So at our Friday’s class, we weren’t sitting in a circle like usually, so he was definitely looking. We walked out of class together at the same time but he stop outside and I was walking to my dorm but my friend told me to wait for her class to finish so we can go and eat. And I saw him watched me go inside again and he continued to smoke and then he sat inside and after a few minutes he came up to me and was like “text me sometime” 

So my think is have you ever had a guy give you his number? When should i text him and if say what?

P.S. I am sort of interested