Hi Sir,
a lump in the armpit usually points to a Lymph Node swelling. it can be due to multiple reasons from normal to extremely scary depending on other symptoms in the body:
1. do you have fever
2. do you have addictions
3. did you recently have an arm trauma or injury
4. is there weight loss
5. is someone around suffering from infections
6. past disease history
7. family cancer history
Please consult a doctor at the earliest.
Next Steps
Contact me for a chat and maybe we look into this with more history sharing, lifestyle and I can offer a more personalized advice.