Wisdom Teeth - Agonising Pain & White Lump....

It's difficult to tell exactly what's going on, but it sounds like what we call "pericoronitis", an infection just under that flap of gum. If this is the case, the best you can do at home is to rinse around the flap with quite hot salty water, 3 or 4 times. Do this every hour or so for a day, and it should settle down a bit. You may also need some antibiotics if you're having trouble opening your mouth as normal.
But a dentist will be able to tell you for sure when he takes a look. Normally it's just a matter of getting you through until the wisdom tooth is fully grown into position.