What other fish are in the tank?
What is the ammonia, nitrite, nitrate and pH of the tank water?
The fish has cloudy white fins that is normally associated with poor water quality.
I would carefully catch the fish and pull the spike out.
Check the water quality and do a 75% water change and gravel clean the substrate every day for 2 weeks.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Add 1-2 heaped tablespoons of rock salt, sea salt, or swimming pool salt for every 20 litres (5 gallons) of tank water. Keep the salt in there for 2 weeks.
When you do the daily water changes, add salt to the new water before adding it to the tank. Only add enough salt to treat each bucket of water you add to the tank.