How long did it take you to lose that weight? Loose skin is often the result of a crash diet. If you lost weight at a sensible pace (0.5kg to 1kg per week) then it's probably not loose skin.
It's probably best to see a doctor to determine if it's loose skin or not. And if it is there's no need to panic just yet. In many cases the skin just needs a little bit of time to shrink and catch up to your new size, so wait a while and see if your body sorts itself out. Toning exercises help prevent and treat loose skin. Only severe cases need surgery and you'd definitely want to talk to your doctor before determining if that's the most appropriate path to take. There are many lotions and potions on the market that claim to help tighten skin, but the effects tend to be minor and only temporary. If you want to try them feel free, but I wouldn't spend too much cash on them because chances are it's just a fancy moisturiser with caffeine in it.
There's a really good article about loose skin after weight loss here:
Good luck! I hope your problem sorts itself out.