patient who received a vaccination two weeks prior returns to the clinic with a

1. Demonstrating a severe local reaction to the inoculation.
   This would be my initial thought. If the patient says the wound feels itchy, then it's likely that he/she is scratching it, which would impede healing. I'm relatively sure that an allergic reaction to an immunization would be systemic in nature, and such a reaction would occur shortly after exposure to the allergen.

The question is a bit vague, so it's tricky. There are many unknowns--as is the case in practice--but the most plausible explanation for the scenario with the information given is a moderate to severe injection site reaction.