**
1. MDMA is a party drug also known as 'ecstasy' in street form and it could be possible that  it might have caused an URTI [upper 
respiratory tract infection], so in best interest it is wise to see an ENT  specialist for Throat Inspection and also get an chest X-ray done to rule out any Respiratory problem.
PS. also keep in mind that it maybe not due to MDMA, but the filler or some other ingredient or impurity. [possible allergic reaction]
2. because the drug causes 
dehydration, and also the additive effect of party [hot condition/environment] might be causing difficulty in swallowing.
PS. If alcohol was also consumed, it exhibits diuretic effect and might have aggravated the condition
3. good 
oral hygiene, rinse your mouth after every meals, avoid smoking, 
tobacco chewing,spicy/fried foods, have warm salt water gargles.
. take salt,turmeric and embelia ribes in 6-6 gm quantity and mix in 1/2kg water and after filtering, have gargles with it [when still lukewarm]
. sucking to 1gm curcuma zedoaria helps in 
sore throat, also sucking to liquorice has same effect.