Its only been about 2 days since my first gymnastics class and all my muscles are extremely sore. Should I still go today even though I'm still this sore?
The feeling you are experience is Delayed Onset Muscle Soreness or DOMS. It is common for people to experience soreness when they are new to exercise, have restarted after taking a long break, or even are just performing a new movement. It should safe for you to workout again and the soreness will diminish in time.
However, if your pain prevents you from moving, is accompanied by swelling or inflammation, or causes you concern speak with a medical professional.