Allergy. The few symptoms that you described are classical symptoms consistent with allergic rhinitis. The nasal congestion is due to engorgement of blood vessels in the side of the nasal cavity and swelling of the tissue around these vessels (called edema). These symptoms can be treated with otc antihistamines such as Claritin or allegra. If these meds do not help, see an allergist.
Likely allergies. Itchy throat vs. Scratchy throat. If it is itchy with stuffy nose. .. Likely allergies - try some over the counter allergy meds: claritin/zyrtec. If it is scratchy with stuffy nose. Likely a viral upper respiratory infection (cold)... Fluids and chicken soup :)!