When you have green snot does it go away on its own or is that a sinus infection and need antibiotics?

To better and more : Accurately assess what it could be, you will need to go see your doctor for an evaluation. He/she will ask you a few questions, like any headaches, fevers, chills, nausea, vomiting, productive cough, post-nasal drip, excess mucus production, itchy runny nose, sneezing, itchy eyes, ears, and throat, ;nasal congestion, etc. Then he/she will examine you. Don't take antibiotics if you don't need to.

Snot's not enough: Most cases of sinusitis should not be treated with antibiotics. The exceptions are those cases that are particularly severe or prolonged. Green or yellow snot is a fairly standard aspect of having a cold, and not in itself an reason to take antibiotics.