u/Fad1ngAway

I emailed a prof about research and he told me to email him back after last Tuesday, since he would be travelling for two weeks. I sent him an email wednesday morning following up and saying that I’d love to discuss further and I still haven’t heard anything back. Should I be worried (it’s only been 4 business days) that he’s not going to respond or should I wait a bit longer. Also, how long should I wait before sending a follow-up and will I seem annoying for sending one? Thanks :)