Dua after salaam #1

Say three times:

أَسْتَغْفِرُ اللّٰهَ

I ask Allaah for forgiveness.

'Astaghfirullaaha

Then say:

اَللّٰهُمَّ أَنْتَ السَّلاَمُ، وَمِنْكَ السَّلاَمُ، تَبَارَكْتَ يَا ذَا الْجَلاَلِ وَالْإِكْرَامِ

O Allah, You are Peace and from You comes peace. Blessed are You, O Owner of majesty and honor.

Allaahumma 'Antas-Salaamu wa minkas-salaamu, tabaarakta yaa Thal-Jalaali wal-'Ikraam