Brief Answer:
Cause must be investigated.

Detailed Answer:
I read your question carefully and I am sorry about these persistent headache your son is experiencing.

There are many types of headaches. Some of them are primary, meaning no cause can be found, like migraine or tension type headache, some are secondary meaning there is an identifiable cause like sinusitis, stroke, tumor, infection etc, causes can be thousands really.
It might have been helpful if you had provided some more info on your son's headache characteristics like location, quality (throbbing, pulsating, constant, pressure like, sharp, lancinating etc), duration of attacks, other accompanying symptoms like nausea, vomiting, nasal congestion, eye redness, lacrimation, vision issues, increased sensitivity to light and noise etc.
Also previous history of headache, other medications or conditions he might have, family history of headache might be important.

Medication like aleve or kroger sinus relief simply alleviate the symptoms they do not address the cause. They are fine to be used when there are no other worrying symptoms thinking it is a primary headache which will subside. However in your case since the headache is persisting from 2 weeks, he needs an evaluation for the possibility of secondary headache, meaning there is a cause which must be treated. So before recommending other pain killers which simply simply alleviate symptoms he needs a physical exam and if deemed necessary perhaps tests like blood tests and imaging as well. If the cause is found it will be addressed accordingly, say if it's sinusitis he might need antibiotics.
Even if no cause is found and it is a primary headache, the type must be determined and if a chronic case preventive treatment might be considered (like antidepressants, calcium channel blockers, beta blockers etc).

I remain at your disposal for further questions.

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