Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am very sorry to hear about your pup having flat, pick bumps on her chin.
Do your pup's bumps look like the lesions on the dog in the following link's chin?
If so in most cases this is related to chin 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.
Here's another picture of chin acne:
If so 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 her to lick it as it does contain peroxide which could irritate her stomach and lead to vomiting.
Other options are a human acne products, either Hibiclens or Phisohex. 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 her to lick as it also will upset her stomach.
You should clean her chin after eating and dry it several times a day, especially if she is a pup that drools frequently. Moisture makes acne worse.
If her acne isn't clearing it may be deep enough that she 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. Her veterinarian can scrape the area or biopsy a lesion to look for them and get her on oral antibiotics if the topical treatments I mentioned don't work.
Rarely this can be related to a fungal infection, in which case she may need oral antifungal medication such as ketaconazole.
If her lesions don't look like acne, and she is a pup that goes to dog parks, canine day care or plays with many other dogs these may be contagious warts. Do her lumps look more like those in the link below?
If so these are probably contagious viral warts (papillomatosis). These are a contagious, sexually transmitted disease caused by a virus and contracted when a dog mates with or licks/sniffs a dog that is affected by them. They tend to be found on the lips, eyelids, chin, inside the mouth, on the footpads, and in the genital area. They are not contagious to people but they are extremely contagious to other dogs. As such she should be kept away from other dogs so out of doggy day care and dog parks.
In most cases these benign tumors resolve with no therapy needed at all in weeks to months. Rarely these can transform into a malignant variant and don't resolve. These need to be removed surgically with wide margins. If the warts are getting ulcerated, interfere with eating or become uncomfortable we can use an antibiotic, Azithromycin, for 10 to 14 days which seems to hasten their resolution.
If you'd like to read more please see this link for an in-depth article about contagious warts in dogs: http://www.petwave.com/Dogs/Dog-Health-Center/Skin-Disorders/Warts.aspx
Please let me know if you have any further questions.