The push to release connection on the top of the heat sink may be secured with thread lock adhesive, but you should not have to remove it. Push the blue ring downward while pulling upward on the bowden tubing. It may be necessary to work it up and down while you push down on the blue locking fitting. I have to use a pair of pliers to hold the blue ring down while wiggling the bowden tube up and down, as it is rather tiny.
Once you have the tubing removed, check for high friction in the now-released bowden tube. Push filament from the extruder drive mechanism and observe how easily it passes through the tube to the open end. If you do not experience clogging, the problem resides in the heat sink/heat break/heater block area.
It's not uncommon for the nozzle to have an excessive gap between the heat break and the nozzle. This will allow for cooled filament to jam, preventing normal feeding.
From the Prusa support site:
Notice that the collet is visible in the photo and appears to hold a longer section of PTFE tubing. It should enter your heat sink until it bottoms against the recess cut into the metal. If it does not, you have the possibility (slim) of jamming in that locations.
Notice also that the nozzle is not flush against the heater block. The heatbreak is threaded into the block with the nozzle slightly lower than flush. This ensures a proper flow from the entry point to the nozzle. If it is not properly secured at either end, the heat break can bulge with filament that cools and creates the jam.