For more details on patching scenarios, read the MSDN article at https://msdn.microsoft.com/en-us/library/mt593040.aspx.
Once your solution is patched, the original solution cannot be altered until the patch is merged back. To enable the solution again, select the base solution and click on the Clone Solution button from the ribbon. For more details, read the following section of the same MSDN article at https://msdn.microsoft.com/en-us/library/mt593040.aspx#Anchor_4.