Since the lump is hard and not painful and you have tried to massage it with no luck I would contact a doctor.
This sends up red flags for me. I had a lump that was sore and painful for about two weeks. About two weeks later I noticed that the lump was not sore any more and hard. After a needle biopsy (no pain) I was diagnosed with cancer. I was lucky to know my body and was able to have it removed without much harm to body figure and mind. Treatments were carried out and I have been cancer free for 14 years.
I had a neighbor who had a baby about 17 years ago and was diagnosed with breast cancer after birth and she went through treatment. So there are too many what ifs for us to answer and this site. Find a doctor or clinic to check you out.
You will be in my thoughts. Keep us posted.
The other S.