Hello, It is possible to get hard lumps under the skin when injecting insulin.Repeatedly injecting into the same site or near the same site can cause lumps. The lumps or tough skin from repeated injections sometimes are called lipohypertrophy. Rotating  your injection sites and avoiding the scarred areas for at least six months will help reduce the scar tissue at these overused sites.  As far as bruises are concerned, the needle may have clipped a small blood vessel, causing it to bleed and form a little bruise  under the skin.  Do s for avoiding bruises and lumps... .....Don t rub the spot.   ......Maintain light pressure with your finger to prevent bruising.  .....If a bruise does appear, don t use that injection site again until the bruise is gone. .....Wait until the alcohol from the swab has dried completely on your skin before injecting.  ......Inject your insulin when it s at room temperature. Cold insulin hurts.  ....Never use your needles more than once. ....Penetrate your skin quickly.  ....pinch up the skin and inject into the fold of the pinched up skin.   If in spite of injecting properly you bleed tegularly,then you must consult your doctor and look for any bleeding disorder. Thanks