Got my coworkers number

Sooo today I asked my manager how old this guy was I wondered bc he was cute. I did nottt tell her my intentions though but she picked up what I was getting at. Anyways she says he’s a minor and asked him if he has a girlfriend he said no and he wrote his number down for me to have. I was telling her that’d I do it myself but she did anyways, I didn’t want it to give off middle school vibes having someone else tell him that I like it but it’s whatever I got the number. I’m so nervous to text him should I just say hi or what. What if something bad happens between us like we ghost each other and then we have to see each other at work everyday 😭 I now see why people say not to talk to your coworkers anyways what do I do Also when I was at work after I got the number I didn’t say anything to him bc I was so embarrassed and nervous probably the biggest mistake but he also didn’t say anything. After I clocked out I went over to him and said his name and then said I’m gonna text him he said okay bet