Tarantulas are not easy to care for. Depending on the species and their original habitat, they require a certain level of humidity for this and other processes. I do not know the environment you have provided for you spider, so I can not really say anything about the present condition. If you have the environment correct, there should not be much of a problem. If not, I do not know what you can do at this stage other than hope that the spider will be able to finish the molt. You can check the humidity in the tank and possibly raise it if it is not high enough but, if the new skeleton has already dried out, there may be a problem.