Forensic medicine groups mechanical injuries into abrasions, contusions, lacerations, sharp-force (incised and stab) wounds and firearm/blast injuries. The descriptor in the stem - blunt force with no break in skin continuity - points to a contusion.
A contusion, or bruise, forms when blunt impact ruptures small subcutaneous and deeper vessels, allowing blood to seep into surrounding tissue while the skin surface stays intact. Its colour change over days helps in estimating age of injury.
The distractors all involve a breach of the skin: a stab is a sharp, penetrating wound; a laceration is a blunt tear that splits the skin with ragged margins and tissue bridging; a bomb blast causes mixed open injuries with marked tissue disruption.
\[\boxed{\textbf{Contusion}}\]