I noticed a small hard lump on my babys thigh a few weeks after vaccination, is it normal? im afraid that a vein/artery was hit. please help, thanks

Lump after VACCINE: This is not uncommon. The ideal of vaccines is to stimulate the immune system, so a bit of inflammation is actually a good thing. The lump that persists is likely a little bit of scarring in the subcutaneous tissue (think of how a skin scar feels a bit harder than the surrounding tissue). This may or may not go away over time, but is in no way dangerous or problematic.