A bone marrow access device includes a cannula and a sharp stylet removably positioned in the cannula. The cannula defines a distal opening at a distal tip and a side aperture in a side of the cannula, proximally from the distal opening. The stylet has a sharp distal tip and extends beyond the distal opening. A plug is receivable in the cannula distal to the side aperture to seal the distal opening when the stylet is removed. A method of accessing bone includes inserting the cannula and sharp stylet positioned in the cannula into bone； removing the sharp stylet from the cannula； pushing a plug through the cannula and distal to the side aperture to seal the distal opening of the cannula； and accessing the bone through the side aperture. Accessing the bone can include aspirating bone marrow, injecting a substance, or inserting an instrument into the bone.
