Timing cover water leak-Help

I have a timing cover gastket leanking water on the left hand side from the bolt just below the water inlet to the block.
This has come to light when topping up all the fluids, so it will most likely leak when I run the engine.
All the parts are new & have been sitting for over a year.
Is there an easy way to fix this?
Do I need to replace the gasket?
If so can I replace it with out pulling the engine or removing the pan?
Cheers