Is this soft, hard or rubbery?
Does this slips in between your fingers if you hold it?
Is that tender?
Well lymphoma is out of question at this area.
It is most likely to be lipoma or sabecous cyst. Both of them are benign and not dangerous at all.
Just enjoy your holiday and get him seen by doctor when you are back.
I hope this helps you
Please ask for any query
Well actually lymphoma occurs where there are lymph nodes. So in the area he has this swelling there are no lymphnodes so lymphoma not possible.
It can be lipoma which is basically fatty swelling and its benign and treatment is removal of the swelling surgically. Even if it is left there no worries or complications.
The second possibility is the sabecous cyst which forms because of the blockade of hair follicle. Its again is not dangerous. If this get infected it can cause pain. Its treatment is removal also.
There is no other significant possibility of anything there.
i hope this helps you now.