If it's a small blister, and...
If it's a small blister, and the adhesives in the piece are still kind of active, sometimes applying heat directly will work, using an iron and a buffer (wax paper/tin foil/etc) carefully.
Larger bumps are more difficult, but occasionally can be remedied if you make a small slit across the bump and then apply heat.
That's what I remember from the old days, anyway.
The solid one may be a...
The solid one may be a problem as what ever is underneath the blistered veneer be it glue or wood seems to have swollen with the veneer, the one that flexes take hudsonhonu advice although I would go with cutting the veneer then adding glue has heating veneer to repair can be tricky.
Bentply is
probably correct. Particle board is particularly prone to expansion when wetted, and it does not shrink back to its original form when subsequently dried. So, the only solution is to sacrifice the veneer in the damaged area -- perhaps by routing a path of that width along the entire length of the top -- and (after sanding flat the bulged area) fitting a replacement veneer in the cleared area. This operation could cost more than the piece is worth. Making a new top of similar veneer over MDF -- readily available as a 4'x8' sheet -- might be more cost-effective.
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