Lookind at your symptoms,you might be suffering from inflammation in the upper respiratory tract due to irritation by the paint spray which you might have inhaled. Blood in your sputum might have occured due to forceful coughing.As there in inflammation in the upper respiratory tract,there is congestion.And when you cough forcefully,tiny blood vessel might tear due to increased pressure leading to bleeding. You might find relief by taking Analgesic and Anti-inflammatory(like Ibuprofen),Antacid(like Rantac),Antihistaminic(like Cetrizine),Oral Decongestant (like containing Phenylephrine) if you are not suffering from hypertension. Avoid Coughing and blowing your nose forcefully.Avoid cold,oily food.Avoid dust,smoke and other pollutants.Do warm saline gargles.Do steam inhalation.Drink plenty of fluids. In future,have a habit of using facial mask while doing the work of spray painting. After taking the above measures if your symptoms are not improving or if you are again suffering from blood in the sputum,then it would be advisable to consult an Otolaryngologist or a Physician Doctor. Hope this answers your question.Take care.