Hi,
As you said, it is the combination of Vildagliptin and metformin. While Metformin, is NOT known to cause any such side effects as skin rashes, Vildagliptin is a relatively new drug in the relatively new class of drugs DPP-4 inhibitors (including Jenumet -sitagliptin+metformin). This gives a good control of the sugar levels but has UNKOWN side effects, skin rashes is one of the listed side effects in the drug information.
Moreover, if you have been just diagnosed with diabetes, you should talk to your doctor if a milder drugs with less side effects like only Metformin would control your sugar levels.