Mark under my dogs eye

My labrador has had a mark under his eye probably since March. I initially though that it was due to trauma (like a scratch). However, it hasn't gone away. It hasn't increased in size. He suffers from allergies and his skin is commonly more itchy this time of the year. In March he had a mast cell tumor removed on his back leg with a good prognosis and clear margins. I'm a little paranoid now that the mark under his eye might be a mast cell tumor but I'm not sure if I'm over reacting?! If I was to go down the route of checking it would involve him having another anaesthetic to do a punch biopsy which I'm in two minds about as it might not be a mast cell tumor! It hasn't increased in size and doesn't feel particularly "lumpy" it does look inflamed. I've attached some pictures. I'd appreciate any advice! 

Hello!  The science regarding mast cell tumours has changed over the years.  There is no way I'm going to tell you that this is or isn't a mast cell tumour, because grossly (ie looking at them on the dog, in situ), MCTs can look like pretty much anything!  They are great pretenders.  Furthermore, Mast cells often proliferate in places with a lot of inflammation.  In the past, before this was understood,  it was not uncommon to diagnose mast cell tumours that turned out to be lumpy foreign body reactions, and subsequently vanished.  I can remember doing this once in the nineties. However, from what I understand of this case, there may not even be mast cells in this lump!   It sounds as if it would be a good idea to let your vet take a biopsy (they could talk to their friendly pathologist for advice beforehand about how useful it would be and how best to go about it, if they have any doubts). Best of luck and please do let us know what is found!

I should have said, let your vet decide whether to biopsy the lesion.  If they think that it may be inflammatory (eg a bee's mouthparts?), they may wish to go about trying to rule inflammatory conditions out first.