yes bro its a bacterial infection. You can try to uptake some v-c and plenty of water as well get rest, use heat on the site like they said to help disperse the oil and increase the blood flow and enlarge the muscle to help it absorb. Dont wait any longer than 2 days to get medical attention. Also monitor your body temp to see if it climbs, mark the site like he said and watch the redness and look for red streaks.
If you get a high fever, red streaks, nasua, vomiting or just hurt really bad go to the doc right away.
most will subside but not everything you get is clean bro, most stuff containes containamiants I would not use that source anymore since its going to cost you more than just your stuff. It cost you pain, maybe medical expenses and fear, thats not worth it.
Nexttime heat and buy some filters and filter your stuff into a clean sterile vial. I do this with everything. NEVER had a problem since.
good luck bro keep us posted.