Hi there - poor boy
Can you look at his paw? If so, is there anything underneath the pad or inbetween the pads at the top of the paw?
I would take him back to the vets for anti-inflammatories, anti-b's and painkillers as it sounds like he may have an infection. You can still use Silica with conventional meds.
With the silicea I would still be using it BUT do this for the next few hours:
put 2 pillules or tabs in a glass of water, stir very vigorously with a clean spoon, then give a teaspoonful every 15min for up to 2 hours. Then 2 pillules every 3 hours today and 3 x a day tomorrow.
If there is any sign of a head (like a pimple or abscess) stop the Silica and exchange for Hepar Sulphate.
This was Jarvs grass seed a day before it came out -