The only way to tighten your lose skin is to do some exercises and weight lifting. That was my problem before but I don't have time to go to the gym and so I bought my own dumbbells (bestadjustabledumbbellsreviews(dot)com/) and do the exercises at home. You can do the following:
Biceps - curls
Triceps - extensions, kick backs
Shoulders - lateral and front raises
Forearms - wrist curls, reverse wrist curls
Pecs - dumbell press (incline, flat, decline), flyes
Abs - standing dumbell side bends, dumbell crunches
Back - reverse flyes
Hamstrings/Quadriceps - squats, lunges, dead lifts
Calves - calf raises