He's really an adorable boy, I love his markings!
How old is he? It's hard to tell just how good they will do until they are fully mature.
Right now he looks like he does have a little long of a nose with more of a slope than defined stop, but his body looks good and it is really hard to tell with pictures. The standard describes a moderately short nose and most judges all have a different opinion about what moderately short means. I know a little chi who got his championship pretty early, he did really well at some shows and didn't even get a nod at others, he had a very short muzzle and some judges found it to be too short, wanted a longer one. You can always try it anyway and see how you like it. If you find conformation showing isn't for you there are many other titles you can go for such as obedience, agility, and canine good citizen. Just have fun.
~*~Gypsy, Deedlit, Cosette, and Isabeau~*~