RE: Ouch my arse!
If sterile procedure was used mate ie. swabbing and use of clean gear, then I highly doubt that you have an abcess. Also the appearance of soreness and redness so soon is not indicative of an abcess but more likely to be recent irritation of the area causing inflammation. Such as moving the needle around, injecting into a difficult place (maybe not properly in the muscle), injecting BD prop (which can cause probs as its painful and 100mg/ml).
Just monitor for a few days, I would say it is simply going to be sore for a few days but will go away.