Sometimes it can be drivers that are no longer compatible with the latest Win 10 update and the vendors have to catch up.
Can you or have you tried with an external mike ?
To see if the update was responsible, you could perform a repair install and opt for not installing the updates during the procedure and while it won't be long before the updates start downloading, try out Skype then.
A repair install doesn't affect personal stuff or installed programs.
If you don't have Win 10 install media, you can create either a DVD or USB after reading the instructions at
https://www.microsoft.com/en-gb/software-download/windows10When you've done that and with the install media inserted, open Windows Explorer - This PC and double click on the drive.
This will start the process when using a DVD but will open to the files if using an USB, where you would then double click on setup Application.
This takes about 3½hrs on my Toshibas.