Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand that you are concerned about bumps on your pup's chin.
Is this a young dog?
Do his lesions look like the pup in the link below?
If your pup's chin looks like the dog in the link then this may be canine acne. Surprisingly enough although canine acne looks terrible dogs don't seem to be bothered much by it. The acne can lead to scars though if it is severe.
You can try a shampoo called Oxydex to clean the area well once to twice daily. See this link for an example (http://www.entirelypets.com/oxydexshampoo.html )
Don't allow him to lick it as it does contain peroxide which could irritate his stomach and lead to vomiting.
Another option is a human acne product called phisohex. You can clean the affected areas once or twice daily, again being careful to let it sit for a few minutes to allow it to flush out the follicles and not allowing him to lick as it also will upset his stomach.
You should clean his chin after eating and dry it several times a day, especially if he is a breed that drools frequently. Moisture makes acne worse.
If his acne isn't clearing it may be deep enough that he needs oral antibiotics. Or it may be complicated by a demodex mite infestation. These mites aren't contagious and are present in all dogs but in some dogs their immune system is such that they are allowed to proliferate in high numbers. They are more commonly a problem in young dogs. His veterinarian can scrape the area or biopsy a lesion to look for them and get him on oral antibiotics if the topical treatments I mentioned don't work.
Please let me know if you have any further questions.