How long should I wait to respond to him?

A guy I dated last year responded to my message yesterday Things got messy between us and we weren't on speaking terms at all last year. On Monday, I sent him a message congratulating him on graduating, then yesterday he sent me a message saying, Thanks for the congratulations, and then he wished me to have a happy Independence Day. I am trying not to think too much into it, but what should I do at this point?