Lump in right groin, limping while walking, getting bigger, lump on neck. History of arthritis in joints. Treatment?

A couple months ago, I noticed a pea size lump in my rt. groin . I checked there because, after walking for only 15 mins. I noticed pain in my groin which caused me to start limping with pain every step. I thought it was just arthritic pain, as I have arthritis in varying degrees in numerous joints... anyways I noticed the lump getting bigger and so went to see my GP....and will be having a ultrasound in June, another two weeks away. I am asking if I should be suspecting cancer as I now have a small lump on the left side of my neck , as well the growing lump in my right groin. Should I see my Doctor sooner than later again?