It is possible to get swollen lymph nodes in the armpits. This is very common with various simple infections, such as the viruses that cause colds and the flu. If you feel in your armpit and detect a few soft, round, mobile lumps, then these are probably lymph nodes and this is most likely what is going on. Generally speaking, the lymph node swelling will go down over a few weeks and you don't need to worry
about it; however, if you notice a very large lymph node that doesn't go down or that keeps growing then this is something you should talk about to your doctor
, as this can rarely be a sign of a serious medical problem.
If, on the other hand, you notice that the skin in your armpit is reddened or warm, then this might be a sign of a skin infection. Infections particularly of the hair shafts are very common in the armpits. Usually, these clear up on their own simply with good skin hygiene, but if they continue to worsen, they need to be evaluated by a doctor as sometimes antibiotics or drainage of a collection of pus may be needed in order to clear up.