7 days ago dry cough, sore throat. Since 3 days ago cough with yellowish phlegm and pain in chest with deep breaths and back while exhale.?

Possibilities.... do you have a fever? Your symptoms sound like you may have acute bronchitis or even pneumonia. It could be viral or bacterial (bacterial more likely with fever!). You need to see a doctor for diagnosis and treatment. If you smoke, you need to quit to decrease airway inflammation. Good luck!