The ornamental design for a self-sealing bag in box cap assembly, as shown and described.
FIG. 1 of the drawings is a top perspective view of a third embodiment of the self-sealing bag in box cap assembly, showing, in particular the ornamental design thereof in a closed configuration;
FIG. 2 of the drawings is bottom perspective view of thereof;
FIG. 3 of the drawings is a top plan view thereof;
FIG. 4 of the drawings is a bottom plan view thereof.
FIG. 5 of the drawings is a first side elevational view thereof;
FIG. 6 of the drawings is a second side elevational view thereof;
FIG. 7 of the drawings is a front elevational view thereof; and,
FIG. 8 of the drawings is a back elevational view thereof.
The dashed lines show the dental instrument in its environment and form no part of the claimed design.