2/ You may actually just have a bruise on your shins. Look for signs of bruising.
1/ Often referred to as ‘Shin Bang’. Your boots maybe too stiff.
1/ Just wait for your shin(s) to recover.
2/ A Heel Raise will change the positioning of your foot and shin within the boot. This may ease the pain. If you actually have bruising you will need to wait until you have recovered. You may well benefit from softer boots if you suspect that yours are too stff. You can tell if your boots are too stiff if you can’t actually flex whilst stood in them.