What is this!

We found this bump or pimple on our dog. Can anyone tell us what it could be?

Hello and thankyou for this picture.  Well, it could simply be inflammation, in the form of an inflamed follicle - perhaps in reaction to a Demodex mite, which is a parasite of the hair follicles, usually made more likely by illness or by the low immunity of youth.  Other options include an early manifestation of papilloma virus, a different infection - less likely - or allergy, or an autoimmune reaction, an insect bite (fleas or flies?), cancer, or a foreign body reaction.  Most vets would want to check this is it doesn't go away on its own within a few days, or if it is itching (in which case it is unlikely to disappear).   I hope that something there is useful to you.