Sore?

Well heres the picture of the sore I'm planning to go to a vet shortly.
http://www.ipages4u.com/pic/fileforu...AE_46_Pic1.jpg

it's kind of blurry but is it that spot on the left?

Its blurry, because I had to take it with my cell phone. :(
But its the red swollen spot on the left ... I scheduled an appointment to the vet ... He can only see me next sat at the earliest :(

Anyone know if thats mouth rot or not?

I don't know much about that sort of thing, but I'm glad you're taking him in to get looked at.

It is really hard to tell from those pics... can you get anything better?

Def take him to the vet - it IS hard to tell - coud be mouth rot, an infected tooth (or socket) or who knows what else. Wouln't let that one slide.

Could it have been caused from "assist feeding"?

From the looks of it it does look to be atleast the start of mouth rot which as Smulkin suggested can be caused from a broken/injured tooth best to let the vet handle the situation
edit: and yes it very well could have been caused from assist feeding one of the reasons why assist feeding should only be used as a last resort

I think it's very possible it was caused by assist feeding....maybe forced the food in and broke a tooth or something....let us know what the vet says.