How to make this shade of white look less "dirty"?

Question

I have a picture of a blanket:

When I try to open up the Color Adjust panel on Sketch and try fooling around with the brightness and contrast, it makes some of the parts look overexposed.

Is there a better way to make them look cleaner without having to retake the picture? I want a white similar to this:

P.S. I have both Sketch and Photoshop

Answer 1

With Photoshop's Image > Adjust > Curves you get this:

Use eraser or white color to clean the unwanted stray dots. Some light details vanish, you must recreate them manually. You can have the edge in another layer, if you want it.

Another version:

The whitening has been made at first fully, stray dots were cleaned by painting white, the whitening has been taken back with the curves a little to get some greyness and the edges of the underlying original were partially revealed with the eraser which had low opacity.

The missing pink cloud must be recreated:

It's here actually the yellow one selected with the magic wand and copied & pasted to a new layer, then recolored with Image > Adjustment > Hue & Saturation

Answer 2

• Duplicate the image layer and press Cmd + Shift + L Mac or Ctrl + Shift + L Win to apply Auto Levels

• Duplicate this layer and go to menu Image > Adjustments > Desaturate

• Press Cmd + L Mac or Ctrl + L Win to open the Levels Window options

• Move the shadow and highlights sliders to remove the midtones

• Use the brush to clean up the noise

• Go to menu Select > Color Range > choose Highlights to select all the white area
• Delete this layer
• With the selection active make a Solid Color layer filled with 100% white

• Change the blend mode to Screen and reduce the opacity
• Click the mask thumbnail to edit it
• Go to menu Effect > Blur > Gaussian Blur = 1 px
• Use the brush with 100% black to unmask the pink cloud and top star

Result

Answer 3

I wouldn't use Sketch for this, because it's not a raster image editor, and any adjustments you can make will therefore be extremely limited.

Use Photoshop instead. Convert the image into LAB mode, and make Levels adjustments as shown below for each of the Lightness, A and B channels. Using LAB mode to do this will enable you to make levels adjustments while keeping the light pink cloud and star.