When cycling my bottom bracket sometimes starts to make a clunking noise, I can get rid of the noise normally by doing one or two strong pedal strokes. Is this anything serious does the bracket need to be looked at?
First, it may not be your bottom bracket. Creaks and clunks are notoriously difficult to localize. If you can reproduce it with the bike on a stand (or upside down on the ground), it may be easier to know for sure.
If it is your bottom bracket, you should replace it (or less commonly, replace only its bearings, depending on the type of bottom bracket).
If you continue to ride, eventually it will probably get worse, but this won't harm anything other than the bottom bracket, so it's not particularly urgent.