What could this sore be on my dogs foot (pic included)

[fizzytonicplease]

I have just noticed this lump on My springer/choc lab cross dogs paw, it's red and looks very sore. However he doesn't seem bothered by it and hasn't been licking it, can't get to the vets today and just wondered if anyone on Mn could help? Sorry the pics are that clear, it's right between his skin and the nail. I did wonder at first if it was a tick however tried to get to it and I'm pretty sure it isn't.