Hi,Dear,thanks for the query to HCM virtual Clinic.
I studied your query and understood your health concerns.
The worry of the lump on your right upper arm,is only due to the fear of it being cancer,as your grandma had
breast cancer.
I reassure you,after studying the details of your query,that you shoud not worry for possibility of cancer in your right upper arm.
Your lump appears to be a unknown insect bite.Possibility of it being boil or sebaceous
cyst is not there as the history is short.
Hope this would resolve your query.
Welcome for any further query in this regard.
Write good review and hit thanks,if this reply helps you.
Have a good day.
Dr.Savaskar M.N.