Make sure its washed everyday. the frenulum (stringy bit) can sometimes become inflamed and sore. normal goes after a few days if this is the case.
More than likely hygiene.
You pull it back and wash daily? All around inside and out?
If yes then you should see a doc.
Hi please use lube ie KY Jelly that will stop the foreskin to be tight , it will also help in pulling it back , may i suggest you seeing your Family Dr , He/she will help you all they can , Take care ,