[Machine] Wash the place. If you do not see it, pour water around it. Indeed, I have seen myself rubbing it from the garment of the Messenger of Allah ﷺ and then praying in it.
تَغْسِلَ مَكَانَهُ فَإِنْ لَمْ تَرَهُ نَضَحْتَ حَوْلَهُ وَلَقَدْ رَأَيْتُنِي أَفْرُكُهُ مِنْ ثَوْبِ رَسُولِ اللهِ ﷺ فَرْكًا فَيُصَلِّي فِيهِ