My DD1 got it after her 1st DTaP. It lasted about 6 weeks and didn't seem to bother her. She got her 2nd DTaP (we vax on schedule) before it had gone but never got a lump after the 2nd or 3rd shots. DD2 got a hot, hard, swollen, obviously very painful reaction to the DTaP (i'm sure it was the T element, i get exactly the same reaction in my arm after a tetanus booster) the first time which went away after 90 minutes (it was literally here and bad and then gone with nothing left to see within 6 or 7 minutes!), but not the 2nd or 3rd.
If you're worried you should cal the doc who did the vax and talk to them.