Hi, I remember when my first daughter got this around 10 months, and it drove me nuts because her fever was so high and she was so uncomfortable. She pointed to her mouth, while crying and thats how I found the bumps inside there.
To help her symptoms, I gave her Motrin and Tylenol (alternating) for pain and fever - and lots of popsicles, and yogurt, as she wasn't hungry for anything else (reason is it hurts to eat).. It is VERY COMMON, and is very contagious so she probably got it from another kid who would've shown no symptoms at first. It led me to stay away from child play areas, as they are breeding areas for illness. It's not just the runny noses, and unwashed hands, but also dirty diapers (they say HMFD can be picked up from this, as babies can put hands in diaper).
The good news is that once they get it they rarely have it again. Be EXTRA careful with your other children and have everyone wash hands even more than normal. The HMFD is a coxsakievirus, see: http://www.kidshealth.org/parent/infections/bacterial_vir...
Also, just a heads up.. my daughter not long after this virus, got something similar, but it was called Roseola, which is marked by a very high fever with no other symptoms, except when the fever breaks, she got a little rash.
Hope your little one is doing better soon!! It usually lasts 3-4 days. Best wishses, Linda