Hi Mummytotwo,

Subungal melanoma is quite rare and there are other reasons that could account for the nail discolouration so please don't think the worst just yet. I don't think your knee/leg pain will be associated - did you tell your GP about it? If your nail did have a melanoma underneath, it wouldn't cause swelling or pain in your leg - painless lumps are the more obvious way melanoma spreads. 

All I can suggest is that you distract yourself throughout the wait for your appointment as I know how worrying it is. Don't use Dr Google as it's not up to date & only gives worse case scenarios. If you need further information on this please look at this (CRUK) website or the Macmillan and British Association of Dermatologists websites as they are more up to date.

Good luck and please let us know how you get on,

Angie (melanoma patient)