There is weird artifact inside my model its not letting me sculpt properly! I made a rat head model from a quad mesh. Then I downloaded an fbx model and deleted its rig armature, resized it and put the rat head on the models head, and booled them together. I sculped the whole body without any problem but ehen i tried to smoothen the joining part of the head to the body. It didnt go well! I just cant smoothen the junction. What do i do? + later i checked that the quad mesh caused some artifacts when i booled them togather  [![i cant smoothen and join this area][1]][1]
[1]: https://i.stack.imgur.com/B9IsW.png![enter image description here](https://i.stack.imgur.com/T921Q.png)
using the simplify brush and smooth you should be able to smoothen the transition.

Another possibility would be some uneven normals or just a corrupted boolean operation. Therefore check out your normal direction and check your topology in wireframe view.

if none of those are helping, pease upload some further details by editing your question. Uploading a file is often also helpfull.