Are swelling and hard lumps normal in healing from gynecomastia surgery?

Most likely, this is residual swelling after your surgery which could persist (especially if you have stopped wearing your garment for a few months) for 6-12 months following surgery. Also lumps may appear when there is scar tissue under the skin.

Firmness and irregularities are not uncommon in the early post operative period. As swelling resolves these areas may sometimes become more apparent. Your result will be evolving over the next several weeks. I generally discourage patients from passing any judgement in the first few weeks as healing is the priority at this point.
Should any of your concerns persist beyond 6 months, you can discuss revisionary options at that point.
As always, discuss your concerns with your board certified plastic surgeon (ABPS).

The area may seem seem uneven as the healing occurs but should ultimately become even. Follow the post operative instructions of your surgeon.