Check for any lump in your armpit or any lymph node swelling.
Yeah,it could be because of hormonal disturbance.
It may be due to infection if you have any other related symptoms like gastric or any infection related symptoms.
But if it doesn't subsude even after menses, so you need to get it checked.
Next Steps
Get it checked by your GP if ut doesn't go.
Health Tips
Maintain the water balance atleast 4-5 litres of water a day. If it is due to infection then it'll definitely resolve, don't worry.
Otherwise you can consult me online.