Heat, swelling, redness, pain and discolored discharge are all common signs of infection. I suggest that you see a doctor right away. The clear retainer you put in was probably not safe: neither clean
http://care.piercing.org/ explains most of what you need to know in terms of care and feeding. Risks vary depending on the skill of the piercer and the quality and sterility of the equipment and jewelry
Although you will need to be particular about the aftercare http://care.piercing.org/ you should still be able to heal this. Sweat tends to cause less irritation than sleeping on the piercing, for example
Bumps like this could be pyogenic bacterial infection, especially with the yellow color to the discharge. Often a piercing done with slightly irritating shape or material like steel or an alloy of
http://care.piercing.org/ has been the most successful approach to aftercare for an oral piercing for me and my clients. Speak to your doctor before you take anything for a piercing. In my experience

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