My dog is having some strange symptoms…?

my dog (a poodle/chihuahua mix) came back from the groomer’s on saturday and he’s been acting strangely since then. he got a haircut and a nail trim. i noticed two small new black spots on his side (his fur) that i haven’t seen before. (when his hair is long, it’s black. but when we cut it, it’s all light grey. therefore the black spots are very obvious now.) under this spot he has a very strong “tickle spot” (even if i rub my hand over it while petting him, his legs go into spasms. he has another one adjacent on the other side.) he’s also been biting and chewing his paws a lot lately, something he rarely does. lastly, his rear end seems very itchy, as he is constantly stopping, sitting, and trying to scratch it. i don’t know if any or all of these symptoms tie together, but what could be wrong with him?

i know i need to take him to the vet, but if you could please help me until then, i’d appreciate it. thank you!