Hi, I'm 22 years old and have the same problem. I have this pea sized lump in my left underarm. I noticed it just a week ago. It's not painful when I touch it but it is very hard and it does not move. I just had a cold for about a month. And I did take Zyrtec (allergy medicine) for my cold. Is this a swollen lymph node? If so, how long will the lump go away? Thanks.