Post a couple more pictures showing the fish from different angles. I want to see if there is a bubble or it's just a white patch.
The creamy white film and white patch is excess mucous that is produced by the fish to protect itself from something that has injured it. It only appears to have excess mucous over the front half of the body, which suggests an injury. If the creamy coloured mucous covered the entire body I would say there's a water quality issue. It might have been burnt by the aquarium heater.
I would clean the tank and monitor the fish for a few days and see how it responds. If the area goes red, that is a bacterial infection. If it gets white fluffy stuff, that is a fungal infection. Cleaning the tank should help reduce the chance of infection.
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Do the following for this issue, or if a fish gets sick or dies.
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.
Do a 75% water change and gravel clean the substrate every day for a week. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in. It also removes a lot of the gunk and this means any medication can work on treating the fish instead of being wasted killing the pathogens in the gunk.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.
Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.