That piece I wrote basically has everything you can attempt... but time is of essence here... you cannot afford to wait more time.
try the following:
1- apply a sugar paste(a bit of sugar mixed with water) or honey and see if there's any effect- Osmosis should make the fluids causing the swelling to leave the hemipene- if it goes down in size, with a big probe(not a small one- a big one that cannot puncture the tissue) try and gently coaxing the hemipene back inside(the right direction is down towards the tip of the tail.
2- if that doesn't work, try using a bit of ice- that should help with the swelling.
3- a salve against hemorrhoids- it may sound funny, but it can actually help -allot- with reducing the tissue's swelling -and- it is a mild antibiotics against infections.
If those methods do not work- you need to see a vet- with all haste. If you can show the vet this article(as I worked with a vet on it all) it may save you allot of time and perhaps even save your snake- great care should be given to the dosage of the anesthetics- the use of a small catheter to reinsert the hemipene was very efficient... sadly we didn't come up with it immidiately.
What ended up killing Spiritus(the Boa who had the hemipene prolapse) was the recovery from the anesthetics- go to a vet who -knows- their stuff.
I hope the first two suggestions will work out though and save the need for amputation/surgery.
If you have to wait until you can go too see a vet(time is of an essence here mate... do not linger unless there's no way around it) keep the tissue moist at all times- a salve for hemorrhoids being applied would be the best option as the antibiotics will give a much needed added protection...
Best of luck, keep us posted.