Bro ... thankfully you only did one shot, so you can stop right now, and you will be fine.
Short term plan...
If you feel like you have seriously maxed out as far as natural training goes, and you fully understand how to grow (proper diet, training and rest), then do this... here is your homework. Over the course of 1 month... Research these following subjects
HPTA
Testosterone
Estrogen
Aromatase Inhibitors (arimidex for example - to search on)
SERMS (nolvadex for example - to search on)
HCG
I would also suggest going over these steroid profiles as much as possible until you have a good understanding of the pros and cons of each, and how they all differ from one another...
Testosterone (all kinds)
Deca Durabolin
Dianabol
Anavar
Primobolan
Winstrol
Equipoise
Many people will say you should only really be worried about test, but research them all, and you can decide what will be best for you for a first cycle.
This forum is a great place to start. Pay special close attention to "first cycle" posts, with people asking for advice. BE SURE to spend lots of time on the POST CYCLE THERAPY FORUM!! THis is very important. See what people are running for PCT protocols. If you do some good research, you can can get up to swing pretty quickly bro... on the basics anyways. You may think that we sound like pricks right now, but you will thank us later.
Good Luck,
Mavy