I agree with the comments made by JohannesD. It is easy to see that your tripod moved, when you magnify the picture of the stars. You can clearly see that the star trails are not small circle segments, instead they have an irregular curvature which is indicative of tripod movement instead of the usual trail casued by the rotation of the Earth.

It is possible to correct for the unsharpness using post processing. In this case it's easier than usual as you can use the star trail as the so-called "point spread function". Each single point of light should have affected only one pixel, but unsharpness causes a brightness profile that affects a group of nearby pixels, this is called the point spread function and knowing this allows you to deblur the image. Ideally you should use the average of a few stars. Also in case of motional blurring, it's best to carve up the image into small parts and deblur each part separately using point spread functions that apply for that part (in case of rotational movement the point spread fucntion will not be uniform).

This is your original image:

Using just the brightest star as the point spread function and deblurring the entire image with that gives the following result:

This was done by splitting the image in its 3 color components and then applying 25 iterations of the Richardson–Lucy deconvolution algorithm using the brightest star at the top left of the image as the point spread function. There are some "ringing" artifacts visible at the high contrast edges of the picture. Also the right hand part isn't that sharp.

Sharpening has made more of the weaker stars visible in the picture. A dim star that has become a smeared out trail in the unsharp image may have a surface brightness that barely exceeds that of the background while in the sharpnened image it will be represented by a sharply peaked brightness function.