Niko, on the whole the image is ok. The blue nebulosity is a fact of your camera filter, so you could change that by desaturating you blue highlights and push in more red. It would need to be done selectively to prevent the background getting a poor caste to it.
Your image is also quite clipped. The sky should not be jet black, it should be a grey tone or light blue. Green in the image usually helps contribute to this colour but you can use shadows and highlights or curves to prevent clipping and manage the colour caste.
You have some differential flexure in your image. Not much but enough to be annoying. Hunt that down first I reckon.
To me the image also looks a little out of focus, be particular about focus and check it every hour early in the night. Using a Bahtinov mask will help and produce excellent results. The focus will shift just a little over the course of the night and that makes for slightly out of focus shots.
There is no apparent star colour either. Maybe take a look at Ken crawfords or Louie's processing tutorials. You will learn a lot through those Tuts and your images will improve almost over night.
Good start, looking forward to more images in the future.
